Here I have white button mushrooms growing on coffee grounds that were scavenged from a local coffee shop.
I spread some innoculated grain over the surface, made sure all was moist, but not wet and covered them to keep them moist and warm. To house them I am using a $10.00 mini greenhouse from Bunnings and placing them in a repurposed cupboard (though I took them out to take these pics).
These pics were taken after 4 days, and in pic 2 you can see the mycelium (the white fuzzy stuff) forming around the grains.
The source material is commercially available from most hardware stores. The range they stock is ‘Mr Fothergills’ which come in packs like seeds.